Gallium oxide (Ga2O3) is an oxide of metal gallium, a Ga2O3 metal-oxide-semiconductor field effect transistor (MOSFET) is advantageous in its stable chemical property, high pressure resistance, low loss, low power leakage, high temperature resistance, radiation resistance, high reliability, and low production cost, and is widely applied in devices, such as, power supply systems, electric vehicles, hybrid vehicles, large-scale devices in plants, photovoltaic power generation systems, air conditioners, servers, personal computers, etc. In order to decrease the power leakage of the gate during preparation process of the Ga2O3 MOSFET, atomic layer deposition (ALD) is generally adopted to grow Al2O3, HfO2, SiO2, and compounds thereof, or plasma enhanced chemical vapor deposition (PECVD) is generally adopted to grow SiN and compounds thereof, on the upper surface of the gate region as a dielectric layer, however, because lattice mismatch and interface defects exist between the dielectric layers and Ga2O3, the performance of the MOSFET is lowered.